Powertrain provided with an optimised LPG injection system

Abstract

The invention relates to a powertrain (1) with indirect LPG injection, comprising a cylinder crankcase (2) on which a cylinder head (3) is mounted, which cylinder head comprises at least two intake pipes (4) each leading into a cylinder (8), the powertrain comprising at least two LPG intake manifolds which lead into the intake pipes (4). According to the invention, a free end of each intake manifold (25, 26, 27, 28, 29) via which the LPG is released is placed in the injection pipe (4), and the free end comprises a dispersion device (30, 35, 39) for releasing LPG over a wider area of the intake pipe (4), the dimensions of which are greater than those of a cross-section of the intake manifold (25, 26, 27, 28, 29).

Description

Description Title of the invention: Powertrain with an optimized LPG gas injection system

[0001] The present invention relates to a powertrain with an optimized LPG (Liquefied Petroleum Gas) gas injection system.

[0002] More specifically, the invention relates to a vehicle powertrain with indirect injection of LPG gas, which may include in particular a spark-ignition engine of the supercharged type, or alternatively of the atmospheric type, i.e. naturally aspirated. This powertrain includes a cylinder block on which is mounted a cylinder head, in which air intake ducts have been hollowed out which open into cylinders. The cylinder head has a so-called "intake" face against which is fixed an intake distributor capable of directing air and / or intake gases towards the intake ducts hollowed out in the cylinder head and connected to the cylinders, and a so-called "exhaust" face against which is fixed an exhaust manifold to recover the burnt gases resulting from the combustion in the cylinders of the engine.The air and / or intake gases are directed towards the intake manifold, having been previously compressed by passing through a compressor which may, for example, constitute a compression stage of a turbocharger, in the case where the engine is of the supercharged type.

[0003] In order to improve the efficiency and performance of the powertrain, the compressed intake air is cooled before being admitted into the engine cylinders. Thus, a cooling stage is installed in the air intake circuit upstream of the cylinder head, taking into account the direction of circulation of the intake air. This cooling stage comprises, for example, an air / water exchanger of the W-CAC (Water Charged Air Cooler) type through which the hot compressed air transfers part of its heat to water or a coolant. This heat exchanger is housed in a casing which is extended downstream by a mounting flange, taking into account the direction of circulation of the intake air, forming a chamber with, for example, a recess in the cylinder head. Said chamber forms an intake manifold plenum.

[0004] LPG indirect injection powertrains have an LPG gas injection duct in the air intake circuit. Injection is generally carried out upstream of the engine cylinders in air intake ducts dug into the cylinder head. Thus, LPG gas injection pipes are pierced from an intake face of the cylinder head to open obliquely into an air intake channel. The LPG gas is thus mixed with the intake air before its introduction into the cylinders, which is controlled by intake valves. Each cylinder is delimited by a cylindrical side wall, a piston and a bottom wall of the cylinder head.

[0005] Publication FR-A1-3112575 discloses a gas injection rail which carries at least one metal tubular sheath capable of housing and supplying fuel to a fuel injector, more particularly an LPG gas type fuel. The liquid gas is contained in a tank and is brought to a pressure reducer. It is then conveyed to the engine intake via the injection rail connected to the injectors which each have an injection end opening into an air intake channel hollowed out in a heat engine cylinder head. However, this injection end is not specially designed to precisely guide the LPG gas into the intake ducts hollowed out in the cylinder head.

[0006] A powertrain according to the invention has a system for indirect injection of LPG gas into the injection ducts located upstream of the cylinders, comprising well-controlled guidance.

[0007] The subject of the invention is a powertrain with indirect injection of LPG gas, comprising a cylinder block on which is mounted a cylinder head comprising at least two intake ducts each opening into a cylinder and intended to supply said cylinders with LPG gas, an intake manifold placed against the cylinder block upstream of said intake ducts, and an LPG gas supply circuit comprising a ramp provided with at least two injectors each extended by a tube fixed to the intake manifold and opening into an intake duct.

[0008] According to the invention, a free end of each tube through which the LPG gas is emitted is placed in the injection conduit, said free end comprising a dispersion device for emitting LPG gas over an enlarged area of ​​the intake duct, the dimensions of which are greater than those of a cross-section of the manifold. Such a dispersion device aims to eliminate certain angular dispersions linked both to the structure of the manifold and to its mounting on the intake manifold. Generally, these manifolds are bent and are therefore conducive to emitting LPG gas into the intake ducts with a certain dispersion. The LPG gas emitted by the manifolds no longer leaves them in the form of a directional jet, but in the form of a dispersed and therefore enlarged jet, making it possible to homogenize the spatial distribution of the LPG gas flow in the intake duct. Thanks to this dispersion device placed at the end of each manifold, the LPG gas will penetrate into the cylinder with greater efficiency in order to improve the efficiency and performance of the powertrain.A powertrain according to the invention comprises an air intake line which may comprise a compressor and a device for cooling the compressed air. The intake distributor makes it possible to convey the compressed and cooled air to the cylinders of the powertrain via the intake ducts. The LPG gas is injected into the intake ducts at the same time as the air, and comes from a gas circuit which is parallel to the air circuit passing through the supply ducts. The pipes are rigid and are preferably made of steel. The passage of the air / LPG gas mixture into each cylinder is managed by at least one intake valve.

[0009] According to a particularly advantageous characteristic of the invention, each intake duct ends in two distinct and separate intake sub-ducts, the free end of each tube being placed in the intake duct in an area located upstream of said two intake sub-ducts and in a central area of ​​said intake duct so that the dispersion device can supply LPG gas to said two intake sub-ducts. This dispersion device placed at the free end of the tube makes it possible to emit LPG gas homogeneously towards the two intake sub-ducts, thus preventing an accumulation of LPG gas from forming in one of said two intake sub-ducts, with the major risk of a possible reflux of LPG gas into the intake duct.

[0010] According to a possible characteristic of the invention, the dispersion device is a part secured to the free end of each tube and comprising a main channel and two secondary channels in fluid communication with said main channel, and each intended to supply LPG gas to a specific inlet sub-duct. The main channel is intended to extend the tube, and the two secondary channels originate on said main channel and are oriented in such a way that they can homogeneously supply the two sub-ducts. The part having the main channel and the two secondary channels acts as a relay part, making it possible to guide and direct the flow of LPG gas emitted by the tube without interacting with the gas flow. The two secondary channels can be either curved or rectilinear. They can also have the same cross-section or have different cross-sections.Preferably, the main channel and the two secondary channels are cylindrical. They can: - either be materialized by separate sub-pipes emerging from the pipe, - or be dug into a solid part, and in this case, said part is similar to an LPG gas distribution nozzle.

[0011] According to a possible characteristic of the invention, the main channel is placed in the continuity of the tubing and the two secondary channels originate on said main channel while being oriented towards the two sub-ducts of the intake duct. The main channel is located upstream of the two secondary channels, the term "upstream" being used in relation to the direction of flow of the LPG gas in the tubing. In other words, the LPG gas first passes through the main channel before moving into the two secondary channels. The gas flow arriving in the main channel thus separates into two distinct flows due to the presence of the two secondary channels.

[0012] According to a possible feature of the invention, the two secondary channels extend from the main channel, diverging from each other. In this way, the two secondary channels are not parallel and are each directed towards a very specific inlet sub-duct. In other words, one secondary channel is directed towards one inlet sub-duct and the other secondary channel is directed towards the other inlet sub-duct.

[0013] According to a possible characteristic of the invention, the two secondary channels form an angle between them which is between 30° and 70°. This angle is in particular a function of the positioning of the two intake sub-ducts relative to each other.

[0014] According to a possible characteristic of the invention, the two secondary channels form an angle between them equal to 50°.

[0015] According to a possible characteristic of the invention, the two secondary channels each have a constant cross-section but which is different from the cross-section of the other secondary channel.

[0016] According to a possible characteristic of the invention, each tube has a rectilinear segment at the end of which the dispersion device is secured, the length of this rectilinear segment being between 5 mm and 15 mm. This rectilinear segment makes it possible to homogenize the gas flow in the tube, just before it enters the main channel and then separates it into two gas flows due to the presence of the two secondary channels of the dispersion device.

[0017] According to an alternative embodiment of a powertrain according to the invention, the dispersion device is constituted by a frustoconical end segment, one inlet end of which has the same dimensions as those of the cross-section of the free end of the tubing, and one outlet end of which has at least one dimension which is greater than those of said inlet end, the inlet end making it possible to connect the frustoconical end segment to the tubing. In this way, by way of example, assuming that the inlet end is circular in shape, the outlet end may for example be oblong in shape, with a major axis which is greater than a diameter of the inlet end and with a minor axis which is less than or equal to said diameter.The outlet end of the truncated end segment can have any shape, the main thing being that it can promote dispersion of LPG gas in a given direction and over a wider area.

[0018] A powertrain according to the invention has the advantage of being more efficient and having better performance than the groups existing powertrains, thanks to a judicious addition of a dispersion device at the free end of the LPG gas supply pipes of the air intake ducts of said powertrain. It also has the advantage of offering additional functionality through the presence of these dispersion devices while remaining the same size as existing powertrains. Finally, it has the advantage of being able to be easily declined in several versions, thanks to a simple structural readjustment of the LPG gas dispersion device located at the end of the pipe.

[0019] A detailed description of three preferred embodiments of a powertrain according to the invention is given below, with reference to the following figures:

[0020] [Fig. 1] Figure 1 is a side view of a part of a powertrain according to the state of the art,

[0021] [Fig. 2] Figure 2 is a perspective view of a powertrain according to the state of the art,

[0022] [Fig. 3] Figure 3 is a side view of an area of ​​a state-of-the-art powertrain, including an intake air cooling device,

[0023] [Fig. 4] Figure 4 is a perspective view of an area of ​​a powertrain according to the state of the art, showing LPG gas supply pipes,

[0024] [Fig. 5] Figure 5 is a side view of an intake duct of a powertrain according to the state of the art showing an angular dispersion in a first direction of the LPG gas emitted by a supply pipe,

[0025] [Fig. 6] Figure 6 is a top view of the inlet duct of Figure 5, showing an angular dispersion in a second direction of the LPG gas emitted by a supply manifold,

[0026] [Fig. 7] Figure 7 is a side view of an LPG gas supply pipe of a first embodiment of a powertrain according to the invention,

[0027] [Fig. 8] Figure 8 is a front view of the LPG gas supply manifold of Figure 7,

[0028] [Fig. 9] Figure 9 is a perspective view of an area of ​​the first embodiment of a powertrain according to the invention, showing the positioning of the LPG gas supply pipes,

[0029] [Fig. 10] Figure 10 is a sectional view of the end of an LPG gas supply pipe of a second embodiment of a powertrain according to the invention,

[0030] [Fig. 11] Figure 11 is a perspective view of an LPG gas supply pipe of a third embodiment of a powertrain according to the invention.

[0031] A powertrain 1 according to the invention is preferably a powertrain with indirect injection of LPG gas. In the non-limiting example illustrated by the figures, we assume that the powertrain 1 comprises three cylinders 8, of the supercharged type, for example by a turbocharger. However, it could also be a naturally aspirated engine.

[0032] Referring to Figures 1, 2 and 3, a power unit 1 according to the invention comprises a cylinder block 2 on which is mounted a cylinder head 3 in which intake ducts 4 have been hollowed out. The cylinder head 3 has: - an intake face 5 against which is fixed an intake distributor 6 capable of directing air and / or LPG gas towards the intake ducts 4, and - an exhaust face 7 against which is fixed an exhaust manifold (not visible in the figures) to recover the burnt gases from the combustion in the cylinders 8 of the powertrain.

[0033] The air and / or intake gases from an intake circuit of the powertrain are directed to the intake manifold 6 having been previously compressed by means of a compressor, which may for example constitute the compression stage of a turbocharger.

[0034] Referring to Figure 3, in order to improve the efficiency and performance of the powertrain 1, the intake air is cooled after being compressed by the compressor, and before its admission into the three cylinders 8 of the powertrain 1. Thus, a cooler stage 9 is placed in the air intake circuit, upstream of the cylinder head 3 in the direction of circulation of the intake air. This cooler stage 9 comprises, for example, an air / water exchanger of the W-CAC type (from the English Water Charged Air Cooler) by which the hot compressed air gives up part of its heat to water or to a coolant. The heat exchanger is housed in a casing 10, which is extended downstream by a fixing flange in the direction of circulation of the intake air, forming a chamber with, for example, a recess in the cylinder head 3. This chamber forms an intake distributor plenum.

[0035] The power units 1 with indirect injection of LPG gas comprise an LPG gas supply circuit opening into the intake ducts 4 of the cylinder head 3, to allow said LPG gas to mix with air before said mixture enters the three cylinders 8.

[0036] Referring to Figures 2 and 4, an LPG gas supply circuit of a powertrain according to the state of the art, schematically comprises a distribution rail 11 which is supplied with LPG gas by a tank, and on which are fixed three injectors 12, 13 and 14 which are each extended by a supply pipe 15, 16, 17. These three supply pipes 15, 16, 17 are supported by an upper edge 18 of the intake distributor 6. In this way, the LPG gas which is stored in the tank, first passes through the distribution rail 11 before passing through the three injectors 12, 13, 14, then through the three supply pipes 15, 16, 17. These supply pipes 15, 16, 17 are represented by cylindrical pipes rigid, having a constant cross-section along their entire length.

[0037] Referring to Figures 4 and 5, the supply pipes 15, 16, 17 each open into an upstream zone 48 of an intake duct 4. Each supply pipe 15, 16, 17 is curved and ends in a rectilinear segment 19 which is inclined relative to a longitudinal axis of the intake duct 4. This rectilinear segment 19 allows said supply pipe 15, 16, 17 to inject LPG gas into the upstream zone 48 of the intake duct 4, in the same direction as the air passing in said intake duct 15, 16, 17, but in a direction inclined relative thereto. In this way, a mixture of air and LPG gas will enter each cylinder 8 of the power unit 1

[0038] Referring to Figure 6, the upstream zone 48 of each intake duct 4 is extended by two separate and substantially parallel sub-ducts 20, 21, said two sub-ducts 20, 21 opening into the corresponding cylinder 8 of the powertrain 1. Each of said two sub-ducts 20, 21 has a cross-section which is smaller than that of the upstream zone 48, the cross-sections of said two sub-ducts 20, 21 being able to be equal or different within the same intake duct.

[0039] Referring to Figures 1 and 6, several channels 22 are made in the cylinder head 3 so as to each open into one end of a sub-duct 20, 21 of each intake duct 4. These channels 22 are provided to each receive an intake valve 23, 24 intended to regulate the passage of the mixture of air and LPG gas circulating in the intake ducts 4 to the corresponding cylinder 8. These intake valves 23, 24 are controlled so as to be able to occupy only two positions: a closed position for which it prevents the passage of the mixture of air and gas to the cylinder 8 in question, and an open position for which it allows the passage of said mixture. In this way, as illustrated in Figure 6, the ends of the two sub-ducts 20, 21 of each intake duct 4 are each crossed by an intake valve 23, 24.

[0040] Referring to Figures 5 and 6, the existing supply pipes 15, 16, 17 have the disadvantage of inducing significant angular dispersions of the LPG gas emitted by them, said dispersions being essentially due to their structure and their attachment to the upper edge 18 of the intake distributor 6. This angular dispersion can reach a range of plus or minus 7°, both in a vertical plane as illustrated in Figure 5 and in a horizontal plane as illustrated in Figure 6. Such angular dispersion cannot be tolerated, because it is likely to generate zones of accumulation of the air / LPG gas mixture in the upstream zones 48 of the intake ducts 4, which can lead to a reflux of said mixture towards the intake distributor 6.

[0041] In order to better control the conditions of emission of the LPG gas at the outlet of the supply pipes 15, 16, 17, a power unit according to the invention comprises supply pipes 25, 26, 27, 28, 29 each ending in a dispersion device making it possible to emit LPG gas into an enlarged zone of the intake duct 4.

[0042] Referring to Figures 7, 8, and 9, according to a first embodiment of a powertrain according to the invention, the dispersion device is in the form of a nozzle 30 comprising a main central channel 31 and two secondary channels 32, 33 extending said main central channel 31. With respect to the direction of flow of the LPG gas in the supply pipes 25, 26, 27, the two secondary channels 32, 33 are placed downstream of the main central channel 31 and originate on said main central channel 31, diverging from each other. The main central channel 31 and the two secondary channels 32, 33 are rectilinear, and preferably said two secondary channels 32, 33 form an angle of 50° between them.This end piece 30 is mounted on a rectilinear end segment 34 of each supply pipe 25, 26, 27 so that the main central channel 31 is placed in perfect continuity with this end segment 34, and therefore so that the two diverging secondary channels 32, 33 are inclined relative to said rectilinear end segment 34. Once the end piece 30 has been mounted on the supply pipe 25, 26, 27, it makes it possible to emit LPG gas into the upstream zones 48 of the intake ducts 4 in two different directions forming an angle of 50° between them.

[0043] Referring to Figure 10, according to a second embodiment of a powertrain according to the invention, the dispersion device is in the form of a nozzle 35 consisting of a solid and compact part and in which a main central channel 36 and two secondary channels 37, 38 extending said main channel 36 have been hollowed out. With respect to the direction of flow of the LPG gas in the supply pipes 28, the two secondary channels 37, 38 are placed downstream of the main central channel 36 and originate on said main central channel 36, diverging from each other. The main central channel 36 and the two secondary channels 37, 38 are rectilinear, and preferably said two secondary channels 37, 38 form between them an angle of 50°. This nozzle 35 is mounted on the supply pipe 28 so that the main central channel 36 is placed in perfect continuity with this supply pipe 28 and therefore so that the two diverging secondary channels 37, 38 are inclined relative to said supply pipe 28. Once the nozzle 35 has been mounted on the supply pipe 28, it makes it possible to emit LPG gas into the upstream zones 48 of the intake ducts 4 in two different directions forming an angle of 50° between them.

[0044] Referring to Figure 11, according to a third embodiment of a powertrain according to the invention, the dispersion device is in the form of a frustoconical end segment 39 of the feed pipe 29. This end segment 39 has an inlet end 40 having the same dimensions as those of the cross-section of the feed pipe 29, and an outlet end 41 having at least one dimension which is greater than those of said inlet end 40. The inlet end 40 is placed upstream of the outlet end 41 and makes it possible to connect the frustoconical end segment 39 to the feed pipe 29. In this way, by way of example, assuming that the inlet end 40 is circular in shape, the outlet end 41 may for example be oblong in shape, with a major axis which is greater than a diameter of the inlet end 40 and with a minor axis which is less than or equal to said diameter.The outlet end 41 of the truncated end piece 39 can have any shape, the essential thing being that it can promote dispersion of the LPG gas in the corresponding inlet duct 4.

[0045] The dispersion device 30, 35, 39 placed at the end of each supply pipe 25, 26, 27, 28, 29 makes it possible to better distribute the LPG gas in each intake duct 4 so that it can equally supply the two sub-ducts 20, 21. It thus makes it possible to prevent the formation of LPG gas accumulation zones in the upstream zone 48 of the intake duct 4 which would be likely to cause a reflux of the air / LPG gas mixture in said intake duct 4.

Claims

Claims

1. Power unit (1) with indirect injection of LPG gas, comprising a cylinder block (2) on which is mounted a cylinder head (3) comprising at least two intake ducts (4) each opening into a cylinder (8) and intended to supply LPG gas to said cylinders (8), an intake manifold (6) placed against the cylinder block (2) upstream of said intake ducts (4), and an LPG gas supply circuit comprising a ramp (11) provided with at least two injectors (12, 13, 14) each extended by a pipe (15, 16, 17, 25, 26, 27, 28, 29) fixed to the intake manifold (6) and opening into an intake duct (4), characterized in that a free end of each pipe (25, 26, 27, 28, 29) through which the LPG gas is emitted is placed in the intake duct (4), and in that said free end comprises a dispersion device (30, 35, 39) for emitting LPG gas over an enlarged area of ​​the intake duct (4),whose dimensions are greater than those of a cross-section of the tubing (25, 26, 27, 28, 29).,

2. Powertrain according to claim 1, characterized in that each intake duct (4) ends in two distinct and separate intake sub-ducts (20, 21), and in that the free end of each pipe (25, 26, 27, 28, 29) is placed in the intake duct (4) in a zone (48) located upstream of said two intake sub-ducts (20, 21) and in a central zone of said intake duct (4) so ​​that the dispersion device (30, 35, 39) can supply LPG gas to said two intake sub-ducts (20, 21).

3. Power unit according to claim 2, characterized in that the dispersion device (30, 35) is a part secured to the free end of each pipe (25, 26, 27, 28) and comprising a main channel (31, 36) and two secondary channels (32, 33, 37, 38) in fluid communication with said main channel (31, 36), said secondary channels (32, 33, 37, 38) each being intended to supply LPG gas to a specific intake sub-duct (20, 21).

4. Power unit according to claim 3, characterized in that the main channel (31, 36) is placed in the continuity of the tubing (25, 26, 27, 28) and the two secondary channels (32, 33, 37, 38) originate on said main channel (31, 36) being oriented towards the two sub-ducts (20, 21) of the intake duct (4).

5. Powertrain according to claim 4, characterized in that the two secondary channels (32, 33, 37, 38) extend from the main channel (31, 36) diverging from each other.

6. Powertrain according to claim 5, characterized in that the two secondary channels (32, 33, 37, 38) form an angle between them which is between 30° and 70°.

7. Powertrain according to claim 6, characterized in that the two secondary channels (32, 33, 37, 38) form an angle between them equal to 50°.

8. Powertrain according to any one of claims 3 to 7, characterized in that the two secondary channels (32, 33, 37, 38) each have a constant cross-section, but which is different from the cross-section of the other secondary channel (32, 33, 37, 38).

9. Powertrain according to any one of claims 3 to 8, characterized in that each pipe (25, 26, 27, 28) has a rectilinear segment (34) at the end of which the dispersion device (30, 35) is secured, and in that the length of this rectilinear segment (34) is between 5mm and 15mm.

10. Powertrain according to claim 1, characterized in that the dispersion device is constituted by a frustoconical end segment (39) of which an inlet end (40) has the same dimensions as those of the cross-section of the tubing (25, 26, 27, 28) and of which an outlet end (41) has at least one dimension which is greater than those of said inlet end (40), and in that the inlet end (40) makes it possible to connect the frustoconical end segment (39) to the tubing (25, 26, 27, 28).

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